I take a different tact, but there is a reason why... okay, sorta long post coming I feel...
When I got into playing, a big thing for me was that if you were good on pinball, you could win free games. For me, it was all about figuring out the shot that I could hit over and over again, until I could build up enough of a score to get past the replay and earn a free game. I played a LOT of route pinball, and I never really learned about wizard modes or whatever, I was all about figuring out what was the safest way to get past a point threshold so that I could get a free game.
With that in mind, a few tips...
First off, how 'good' you are is related to what you are trying to do. For instance, I've been playing the absolute hell out of my Iron Man lately. I've been going for high scores. To do that, I've been purposely stacking the modes together and trying to play them to earn Jericho and / or Do or Die shots. When I fail in this mission 95%+ of the time, I end up with really small scores.
If I was playing a four player game, this would absolutely NOT be my strategy. Instead, I would go for either Bogey or Monger and try to get a good one of those, knowing that the perfect stack is an extremely difficult goal that my opponents really probably won't get either, and if they go for it I'll win 95%+ of the time.
So anyway, the first thing that I suggest is to learn the ins and the outs of a machine's rules. If you have a machine at home, really try to learn your machine. Set yourself a goal - play through the modes, play through the multiball, etc - and see what makes the most sense for earning points.
Along with this, I would suggest setting your machine so that it does not restart during games, and not restarting during games ever. If you have a bad first ball and you're in a four player game, you have to change your strategy to recover and still have a shot at winning, you don't get a do over.
I've only been in one official tournament, which was actually for the launch of Iron Man, and in the finals for my first two balls, I flipped the ball a total of once. I somehow recovered on my third ball to win the novice division.
Some other stuff...
Figure out what shots are dangerous, and which are not. Weigh those risks and rewards in the game. I really like Viper Night Drivin', which has an incredibly easy center ramp... that is worth almost no points. So, if I'm really close to someone else in points, I shoot that thing 20 times or whatever. But, if I'm far away, I'm not going for that.
Learn the backhand. It's far more important than post passing I think.
Slow your game down. Think about your next shot. That doesn't mean catch the ball every time, but that isn't a bad place to start. My brother-in-law took that on for a while, just catching each ball that came down and then looking at what was flashing and shooting at that, and he instantly got WAY better.
Learn to NOT flip. As long as the ball hits the flipper rubber, it will usually bounce to the other side so it can be caught, aimed and shot.
I never post pass, because I screw it up probably 25% of the time, but I think I'm decent thanks to learning when not to flip and using the backhand to hit other things. If you can post pass, even better. I rarely see people post pass in tournaments, and I've hosted a ton of them at the Midwest Gaming Classic.
Finally, set up your machines tough. Three balls, outlanes open, sensitive slingshots, random awards turned off whenever possible. You'll definitely get better.
Last thing with this, don't make it so that you're not having fun playing. I've had someone suggest to me that I should take the glass off the machine, practice a shot, grab the ball, and then put it in the right place to practice the shot again. To me, that isn't pinball, that's work. And I most definitely do not want to 'work' when I play pinball. Whatever you decide, come up with something that you think is fun and play that way.